Chemical injection is used in oilfield applications to mitigate formation of scale, to counteract corrosion, and/or to treat the produced fluids in other ways to alter chemical properties in the downhole environment. In many applications, a single point chemical injection is performed above or below a production packer. The chemical injection is generally continuous and non-selective, i.e. the amount of injected fluid into a specific zone cannot easily be varied over time and in relation to other injection points in the well. Sometimes injected chemicals can build up in an isolated zone and are potentially damaging to the reservoir and associated completion equipment due to the increasing concentration of foreign chemical constituents. Over-injection also represents a potentially wasteful use of costly specialty chemicals or fluids